1. Field of the Invention
Aspects of the present invention relate to a system for processing and transmitting a digital broadcasting signal and a method thereof, which can robustly process and transmit a digital broadcasting transport stream, and more particularly, to a system for processing and transmitting a digital broadcasting signal and a method thereof, which robustly process and transmit a digital broadcasting transport stream with a simple construction, that strives for the performance improvement through performing an information exchange and mapping on a dual transport stream including normal data and robust data, and which can confirm the channel state using a supplementary reference signal, in order to improve the receiving performance of an Advanced Television Systems Committee (ATSC) Vestigial Side Band (VSB) system that is an American type digital terrestrial broadcasting system.
2. Description of the Related Art
An Advanced Television Systems Committee (ATSC) Vestigial Side Band (VSB) system an American type digital terrestrial broadcasting system and is a signal carrier type broadcasting system. The ATSC VSB system uses a field sync signal in the unit of 312 segments. Accordingly, this system's receiving performance is not good in an inferior channel, and particularly, in a Doppler fading channel.
FIG. 1 is a block diagram illustrating the construction of a transmitter/receiver of an ATSC DTV standard as a general American type digital terrestrial broadcasting system. The digital broadcast transmitter of FIG. 1 is an enhanced VSB (EVSB) system proposed by Philips, which forms and transmits a dual stream. The dual stream is produced by adding robust data to normal data of the basic ATSC VSB system. As illustrated in FIG. 1, the digital broadcast transmitter includes a randomizer 11 randomizing a dual stream. A Reed-Solomon (RS) encoder 12 in the form of a concatenated coder adds parity bytes to the transport stream in order to correct errors occurring due to the channel characteristics in a transport process. An interleaver 13 interleaves the RS-encoded data according to a specified pattern. A ⅔-rate trellis encoder 14 maps the interleaved data onto 8-level symbols by performing a ⅔-rate trellis encoding of the interleaved data. The digital broadcast transmitter performs an error correction coding of the dual stream.
The digital broadcast transmitter further includes a multiplexer 15 inserting a field sync signal and a segment sync signal into the error-correction-coded data as illustrated in FIG. 2. A modulator 16 inserts a pilot tone into the data symbols into which the segment sync signal and the field sync signal have been inserted by adding a specified DC value to the data symbols. The modulator 16 performs a VSB modulation of the data symbols by pulse-shaping the data symbols, and up-converts the modulated data symbols into an RF channel band signal to transmit the RF channel band signal.
In the digital broadcast transmitter, the normal data and the robust data are multiplexed (not illustrated) according to a dual stream system that transmits the normal data and the robust data through one channel. The multiplexed data is inputted to the randomizer 11. The input data is randomized through the randomizer 11, outer-encoded through the RS encoder 120 that is an outer encoder, and then distributed through the interleaver 13.
Also, the interleaved data is inner-encoded in the unit of 12 symbols through the trellis encoder 14, and then mapped onto the 8-level symbols. After the field sync signal and the segment sync signal are inserted into the encoded data, the data is VSB-modulated by inserting the pilot tone into the data, and converted into an RF signal.
The digital broadcast receiver of FIG. 1 includes a tuner (not illustrated) converting an RF signal received through a channel into a baseband signal. A demodulator 21 performs a sync detection and demodulation of the converted baseband signal. An equalizer 22 compensates for a channel distortion of the demodulated signal occurring due to a multi-path. A Viterbi decoder 23 corrects errors of the equalized signal and decodes the error-corrected signal to symbol data. A deinterleaver 24 rearranges the data distributed by the interleaver 13 of the digital broadcast transmitter. A RS decoder 25 corrects errors. A derandomizer 26 de-randomizes the data corrected through the RS decoder 25 and outputs an MPEG-2 transport stream. Accordingly, the digital broadcast receiver of FIG. 1 down-converts the RF signal into the baseband signal, demodulates and equalizes the converted signal, and then channel-decodes the demodulated signal to restore the original signal.
FIG. 2 illustrates a VSB data frame for use in the American type digital broadcasting (8-VSB) system, into which a segment sync signal and a field sync signal are inserted. As shown in FIG. 2, one frame is composed of two fields. One field is composed of one field sync segment that is the first segment, and 312 data segments. Also, one segment in the VSB data frame corresponds to one MPEG-2 packet, and is composed of a segment sync signal of four symbols and 828 data symbols. In FIG. 2, the segment sync signal and the field sync signal are used for the synchronization and equalization in the digital broadcast receiver. That is, the field sync signal and the segment sync signal refer to known data between the digital broadcast transmitter and receiver, which is used as a reference signal when the equalization is performed in the receiver side.
The American type digital terrestrial broadcasting system as illustrated in FIG. 1 is a system that can form and transmit a dual stream produced by adding the robust data to the normal data of the existing ATSC VSB system. This system transmits the robust data together with the existing normal data. However, the American type digital terrestrial broadcasting system of FIG. 1 has the problem that it has almost no effect of improving the inferior receiving performance in a multipath channel due to the transmission of the existing normal data, even though the system transmits the dual stream produced by adding the robust data to the normal data. That is, the robust data has almost no effect of improving the receiving performance according to the improvement of the normal stream.
Also, even with respect to a turbo stream, the robust data does not have a great effect of improving the receiving performance in a multipath environment.
In addition, according to the conventional digital broadcasting system, it is impossible to confirm the channel state between a transmitter side and a receiver side.